button {
    color: black;
    height: 40px;
    font-size: 16px;
    text-decoration: none;

}

button:hover {
    text-decoration: underline;
    color: #007bff;
    text-decoration: underline;
}

ul {
    display: flex;
}

li {

    list-style-type: none;
    /*display: flex;*/
    margin: 5px;
    /*边框*/
    padding: 5px 10px;
    border-radius: 5px;
    text-align: center;
    -webkit-border-radius: 5px;
    -moz-border-radius: 5px;
    -ms-border-radius: 5px;
    -o-border-radius: 5px;
}